1. Field of the Invention
This invention relates generally to wire drawing dies and methods of making such dies, and more particularly to a wire drawing die employing a synthetic hard, wear-resistant material and the method of making the same.
2. Description of the Prior Art
Natural diamond wire drawing dies have been manufactured for many years and typically comprise a metal casing in which the diamond is mounted, the casing in turn being adpated to be mounted in a wire drawing machine. U.S. Pat. No. 2,171,323 discloses one prior method of making a diamond wire drawing die. In another, more recent method of making a diamond wire drawing die, a flat-bottomed cavity is machined in the casing and a layer of powdered metal is deposited in the cavity, the diamond placed thereon, and additional powdered metal is deposited over the diamond. Powdered metal is then deposited in the cavity of a metal plug which is then inserted in the casing cavity. The casing is then heated, as by induction heat or gas firing and pressure is applied to the plug thereby to solidify the metal powder to encapsulate the diamond. The usual countersunk openings are then machined in the back side of the casing and in the plug and the die opening is drilled through the diamond. U.S. Pat. No. 3,978,744 discloses another more recent method of making natural diamond wire drawing dies.
Polycrystalline aggregates of synthetic diamond have recently become available and an annular sintered tungsten carbide blank having a core or polycrystalline aggregate of synthetic diamond is sold by the General Electric Company under the trademark "Compax". In the past, wire drawing dies employing blanks having polycrystalline aggregate of synthetic diamond cores have been shrink-fitted in the casing; however, such shrink-fitting of the blank has required a substantial amount of skilled labor and has resulted in excessive breakage of the synthetic diamond core. Furthermore, a Compax blank in the form of a segment of a circle has recently become available which, because of its configuration, does not permit such shrink-fitting in the casing. Still further, the General Electric Company has even more recently introduced another synthetic hard, wear-resistant material suitable for use in wire drawing dies, that material being polycrystalline cubic boron nitride sold under the trademark Borazon. It is therefore desirable to provide a wire drawing die employing a synthetic hard, wear-resistant material, and a method of making the same, which eliminates shrink-fitting of the blank in the casing and reduces breakage of the core.